The present invention relates to manhole cover assemblies for glass lined steel pressure vessels, and more particularly to a quick opening manhole cover assembly for such vessels.
Glass lined steel pressure vessels are well known in the art and are used, for example, by the chemical and food industry to process various chemicals and food stuffs. Such vessels can be relatively large, ranging in capacity to several thousand gallons, and can be constructed to withstand internal pressures of several atmospheres. It is common to provide such vessels with manholes to permit entry into the vessel for cleaning and inspection.
Usually, the cover for such a manhole is clamped directly to a flange surrounding the manhole opening. The clamps are sized to withstand the load necessary to compress a gasket between the manhole cover and the flange in order to obtain a leak-free joint. It is not uncommon to use many large clamps in order to distribute the load evenly about the manhole cover and to use a hand tool, such as a wrench, to individually tighten each clamp. Use of a hand tool can result in overtightening that could cause distortion of the flange and glass damage. Use of clamps that can be removed or left untightened may result in unsafe conditions. For example, such clamps or the handtool used to tighten the clamps could drop into the vessel and damage the glass lining.
Moreover, in order to secure the cover in the prior art, each clamp had to be individually wrench tightened several times to properly seat the gasket. This procedure could take as long as an hour depending upon the size of the manhole, the number of clamps used and the pressures expected within the vessel. Conversely, to open the manhole cover, each clamp had to be loosened and removed.
The present invention provides a quick opening manhole assembly where the manhole cover can be opened or closed within one minute without using hand tools. No clamps are used to compress a gasket between the manhole cover and the vessel and once an initial seal is made, the pressure within the vessel automatically compresses a gasket for a tighter seal. The quick opening manhole assembly of the present invention is an integral assembly which can be retrofitted to existing glass lined pressure vessels.